1. Field of the Invention
This invention relates to the storage of energy for future use, and more particularly, to apparatus and a method for converting electrical energy during off-peak periods of low demand to hydrogen and oxygen that are stored for later conversion back into electrical energy during peak periods of high demand. It also relates to such a system and method that operates at self generated high pressure for efficient energy conversion and storage of the gases.
2. Background Information
Electric utilities have large installed capacity to met peak demand and the required safety margin. Most of the time, especially at night and weekends, only a fraction of that capacity is required to meet nominal demand. In fact, some of the peaking units operate only a few hours a year. In addition, utilities purchase blocks of peak power on a take-or-pay basis to ensure sufficient power during their highest demand periods, such as mid-summer heat waves. In some instances, bottlenecks in the transmission system complicate the task of delivering power where it is needed during periods of peak demand.
In addition to the problems associated with economically meeting peak demand, utilities have endeavored to improve performance through load leveling in order to operate certain of their equipment at maximum efficiency. U.S. Pat. No. 6,093,306 describes a complex system for abating emissions and providing load leveling for fossil fuel plants. The process produces hydrogen through the electrolysis of water during off-peak periods for use in a fuel cell at the plant to generate electricity during peak periods, which is added to the plant output. While this allows the fossil fuel plant to operate more efficiently and cleanly, it does not address the problems of transmission constriction or peaking.
It has also been suggested that renewable energy sources, such as solar and wind energy, can be used to generate hydrogen gas which is then used to generate electricity in fuel cells during periods when the sunlight or wind is not available or insufficient to produce electricity. Again, neither of these approaches address the problems of transmission restriction or peaking.
There is room, therefore, for improvements in the configuration and operation of systems for generating and distributing electric power.